One application of x-ray backscatter technology is that of x-ray inspection, as employed, for example, in a portal through which a vehicle passes, or in a system mounted inside a vehicle for inspecting targets outside the vehicle. In such systems, an x-ray beam scans an inspection target and detectors may measure the intensity of radiation transmitted through the target, or, else, detectors may measure x-rays that are scattered as the inspection vehicle and target pass each other. During inspection operations where both transmitted and backscattered x-rays are imaged, it would be desirable to switch readily between emission of an x-ray fan beam and emission of a swept pencil beam.
A versatile beam scanner that allows a pencil beam to be swept between variable limits subject to specified constraints, such as conserving fluence incident on a target for different fields of view, is taught in US Published Patent Applications 2012/0106714 and 2012/0269319, which are incorporated herein by reference. In the systems taught in those applications, however, there is no provision for generating a fan beam incident upon the inspected object.
A prior art system providing both a fan beam and a swept pencil beam was described in U.S. Pat. No. 6,192,104, and, in that system, the respective fan and pencil beams are derived from a single source simultaneously, with a necessary angular offset between the respective planes of the fan beam and of the swept pencil beam.